Biological organisms are nonlinear, time-varying systems with many variables. It is generally difficult to obtain clean, simple input-output relationships or low-variance correlation relationships. There is a growing community of workers who believe that the developing field of dynamical systems, especially its best-known areas of chaos and fractals, offers attractive alternative methods to the use of linear systems with additive noise for modeling and studying biological and biomedical relationships. By making low-cost, computer-based materials available to the entire NIH community, we hope to further two goals. One is to allow interested researchers to obtain a fuller understanding of the principles and results available. The other is to facilitate limited trials of particular combinations of processing algorithms, parameters, and data sets to determine if chaos, fractals, or other aspects of dynamical systems might be worthwhile in a given problem area. The NIH Library, a unit of NCRR, agreed to develop a campus-wide resource for chaos and dynamical systems programs for the personal computer world, in cooperation with the Inter-Institute Chaos Council of the NIH.